Modulating system



June 9, 1936. K. SCHUCHTER 2,043,443

MODULATING SYSTEM Filed Dec. 4, 1935 Z-fsaurce/ Patented June 9, 1936 PATENT OFFICE MODULATING SYSTEM Karl Schuchter, Innsbruck, Austria Application December 4, 1933, Serial No. 700,904 In Austria January 16, 1933 6 Claims. (Cl. 179-171) This invention relates to improvements in modulating systems, particularly to such as employed in high frequency modulation, whereby a rectifier without plate tension source is employed.

Modulating systems are known in which electron discharge devices are used. However, for realizing a sufficient effect in modulation, 3. plurality of such devices must be applied. In such modulating systems rectifiers of other types are not employed. The different constituent parts of these known systems are so switched as to form aparallel circuit thus rendering inevitable a great loss in high frequency energy. The elements of such known systems being very numerous and'the energy losses entailed correspondingly high, such systems are in effect uneconornical both from the point of view of manufacture and of service.

vAllthesedisadvantages are avoided by employing the present invention which provides a rectifying device of any kind connected in series with a low frequency source. The low frequency energy having passed through the rectifier, is superposed on the high frequency energy which is induced in a coil connected in series with the rectifier. The high frequency in the coil may, for example, be produced by means of a transmitter inductively coupled with the coil.

With telephonic transmitters the audion frequency currents flowing from a microphone device or an electric pick-up are conducted according to the present invention, to the rectifier after having been passed through a transformer, while an amplifier may be inserted before the latter.

The rectifier may be of any type, with or without hot electrode. In particular a valve rectifier may be employed.

According to known practice, the high frequency energy to be modulated and to which the low frequency energy is superimposed, must be conducted first through the rectifier and then through a special output transformer into a particular output circuit. It is known to accomplish this by employing as a rectifier a threeelectrode vacuum tube which is controlled by the grid voltage in order to prevent a reduction of the modulating effect owing to the fact that the high frequency energy source is influenced by the load of the different circuits.

On the other hand, the oscillations generated by superimposing the low frequency to the high frequency currents, produce, according to the present invention, a modulating effect on the transmitter circuit, forming at the same time the output circuit itself emitting the oscillations.

In contradistinction to known practice this effect produced, according to the present invention, whatever type of rectifier may be utilized.

This contradistinction is important both for assembling the connection system and also for its Working effect, the result of which is not only a different disposition of the output circuit, but also a different manner of influencing the high frequency currents oscillations.

With low power transmitters even a crystal detector may prove sufilcient, according to the invention, for producing the modulation desired. But if the rectifier is omitted, no modulation takes place.

In the accompanying drawing,

Fig. 1 is a diagram of my improved modulating system.

Fig. 2 is a similar diagram of the same in which a hot electrode is employed.

The transformer I is selected for maximum efficiency of the rectifier employed with regard to the source of low frequency. Instead of the detector 2 any valve rectifier may be employed. Preferably the number of windings of the coupling coil 3 should be the same as that of the transmitter coil 4, coupled with 3. This coupling ratio is unaltered after having once for all been adjusted to the highest effect.

The variable condenser 5 which is switched in parallel to the coupling coil 3 is not absolutely indispensable for obtaining the modulating efiect. The transmitter coil 4 is coupled as shown to a load coil 6 arranged for instance in an antenna circuit.

The foregoing description relates particularly to transmitters for telephony, but the system described may also be used in the same manner with different values of carrier frequency and modulating frequency.

What is claimed is:

1. A modulation system for modulating high frequency currents comprising a high frequency source, a high frequency circuit containing a coupling coil, a low frequency source, a modulation circuit comprising a coupling coil and a rectifier for high frequency, the said coil and the rectifier being both arranged in series with the low frequency source, the two coupling coils being inductively coupled together, the coupling between the high frequency circuit and modulation circuit being such that the high frequency is fed to the modulation circuit and the modulated high frequency is fed back into the high frequency circuit whereby the high frequency circuit serves as the output circuit for the modulated high frequency oscillations.

2. A modulation system for modulating high frequency currents, comprising a high frequency source, a high frequency circuit containing a coupling coil; a low frequency source, a low frequency circuit including a low frequency transformer coil, a modulation circuit comprising a coupling coil, a rectifier for high frequency and a low frequency transformer coil, the three said elements being arranged in series, the two coupling coils being inductively coupled together, and the two low frequency transformer coils being the elements composing a low frequency transformer, the coupling between the high frequency circuit and modulation circuit being such that the high frequency is fed to the modulation circuit and the modulated high frequency is fed back into the high frequency circuit whereby the high frequency circuit serves as the output circuit for the modulated high frequency oscillations.

3. A modulation system for modulating high frequency currents, comprising a high frequency source, a high frequency circuit containing a coupling coil; a low frequency circuit including a low frequency coil, a modulation circuit comprising a coupling coil, a rectifier of the hot electrode type and a low frequency transformer coil, said three elements being arranged in series, the two coupling coils being inductively coupled together, and the two low frequency transformer coils forming together a low frequency transformer, the coupling between the high frequency circuit and modulation circuit being such that the high frequency is fed to the modulation circuit and the modulated high frequency is fed back into the high frequency circuit whereby the high frequency circuit serves as the output circuit for the modulated high frequency oscillations.

4. A modulation system for modulating high frequency currents comprising a high frequency source, a high frequency circuit containing a coupling coil; a low frequency source, a low frequency circuit including a low frequency transformer coil, a modulation circuit comprising a coupling coil, a dry rectifier and a low frequency coil, the said three elements being arranged in series, the two coupling coils being inductively coupled together, and the two low frequency transformer coils forming a low frequency transformer, the coupling between the high frequency circuit and modulation circuit being such that the high frequency is fed to the modulation circuit and the modulated high frequency is fed back into the high frequency circuit whereby the high frequency circuit serves as the output circuit for the modulated high frequency oscillations.

5. A modulation system for modulating high frequency currents comprising a high frequency source, a high frequency circuit containing a coupling coil; a low frequency source, a low frequency circuit including a low frequency transformer coil, a modulation circuit comprising a, coupling coil, a rectifier for high frequency and a low frequency coil, said three elements being arranged in series, a variable condenser to influence the modulation and switched in parallel to the coupling coil, the two coupling coils being inductively coupled together, and the two low frequency transformer coils forming together a low frequency transformer, the coupling between the high frequency circuit and modulation circuit being such that the high frequency is fed to the modulation circuit and the modulated high frequency is fed back into the high frequency circuit whereby the high frequency circuit serves as the output circuit for the modulated high fre- 9 quency oscillations.

6. A modulation system for modulating high frequency currents comprising a high frequency source, a high frequency circuit containing a coupling coil; a low frequency source, a low frequency circuit including a low frequency transformer coil, a modulation circuit comprising a coupling coil, a crystal detector and a low frequency coil, the said three elements being arranged in series, said two coupling coils being inductively coupled together, and the two low frequency transformer coils forming a low frequency transformer, the coupling between the high frequency circuit and modulation circuit being such that the high frequency is fed to the modulation circuit and the modulated high frequency is fed back into the high frequency circuit whereby the high frequency circuit serves as the output circuit for the modulated high frequency oscillations.

KARL SCHU'CHTER. 

